feat: add reference voyage terminal assignment gates

[FHoffarth]

Summary

• Adds canonical questions Q-0038..Q-0041 for voyage departure/arrival terminal and berth assignments
• Updates authority matrix in src/timonelo/evidence/authority.py and evidence/registry/document_classes.json
• Implements strict fail-closed gating: generic terminal existence does NOT imply voyage-specific terminal assignment
• Shanghai and Tokyo terminal assignments for MSC Bellissima Oct-2026 sailing remain explicitly UNKNOWN
• No unproven terminal or berth inferences from proximity or discovery candidates
• 79 focused tests pass
• 867 full-suite tests pass
• git diff --check clean